The present disclosure relates to a guide rail structure for a front window in a working vehicle such as a hydraulic shovel.
Generally, some front windows to be provided in a cab of a working vehicle such as a hydraulic shovel are structured to move between a closed position where a window opening at a cab front surface is closed and an open position where the front window is housed in a cab ceiling portion and the window opening is open. Some of the front windows are structured to wind base end sides of assist cables, whose tip end sides are joined to lower portions of the front window, using winders disposed on cab rear portions in order to assist an operator when opening and closing the front window.
In such a front window, guide rails that guide an opening and closing movement of the front window are disposed in inverted L shapes from the cab front surface to the ceiling surface. A conventional guide rail uses a roller guide portion for guiding an upper roller and a lower roller attached to the upper and lower portions of the front window and a cable guide portion for guiding the assist cable that are juxtaposed (for example, refer to Japanese Published Unexamined Patent Application No. 2002-327571 and Japanese Published Unexamined Patent Application No. 2000-274135).
When a cab having, for example, a substantially rectangular parallelepiped shape is provided with guide rails including the roller guide portions and the cable guide portions which are juxtaposed, if the radius of curvature of the guide rail corner portion to be disposed at the corner between the cab front surface and cab ceiling surface is great, the guide rail corner portion projects to the indoor side and reduces the cab interior space or obstructs the field of view of an operator. There is thus a demand to minimize the radius of curvature of the guide rail corner portion. However, if the radius of curvature of the cable guide portion is small at the guide rail corner portion, the frictional force that occurs when the assist cable moves while being pressed against the groove inner side surface increases, and the assist cable and the guide rail are worn out early.
On the other hand, to prevent rainwater from entering the gaps between the front window and the window opening when the front window is at the closed position, a sealing member is fitted to the peripheral edge portion of the front window opening. However, excellent sealing performance cannot be secured unless the front window can be pressed perpendicularly to the sealing member when the front window is closed.
Therefore, in Japanese Published Unexamined Patent Application No. 2002-327571, by providing a sliding member with wear resistance and lubricity or disposing a cable guide roller on the cable guide portion at the guide rail corner portion, the friction which occurs between the assist cable and the guide rail at the guide rail corner portion can be reduced. On the other hand, in Japanese Published Unexamined Patent Application No. 2000-274135, to secure sealing performance between the front window and the sealing member, a device for pressing the front window perpendicular to the sealing member is proposed.